Why grid capacity decides data centre sites in Germany

A data centre needs three things: land, fibre and power. Land can be found and fibre can be laid. In Germany, power is the variable that turns a site into a yes or a no. Anyone assessing a location today assesses the grid connection first. Everything else follows.

Why is the grid connection the bottleneck rather than land?

Because a data centre is a load the grid was not built for at most locations. A campus draws, around the clock, the kind of power that otherwise only heavy industry calls for, from the first day of operation.

The local distribution grid was sized for commercial premises, housing and mid-sized industry. The nearest substation has a fixed transformer capacity, and part of it is already allocated or reserved. New capacity only appears when the network operator builds: a new transformer, a new substation, a new line. That follows grid development plans, permits and equipment lead times, not the timetable of a single applicant.

Land behaves differently. Industrial estates and former industrial sites exist in many regions, a zoning plan can be drawn up or amended, and fibre follows demand. Grid capacity does not, or only years later. That is why it is the criterion on which a site fails first, or passes first.

What does a grid connection request for a data centre involve?

A network operator, a voltage level, a point of connection, a capacity and a timeline. From these five inputs comes the grid compatibility study, and from the study the connection commitment.

Network operator. Smaller loads belong to the distribution system operator, large loads to the transmission system operator. Which one is responsible depends on the capacity requested and the grid structure at the site; each has its own procedure and deadlines.

Voltage level. Small data centres connect at medium voltage. Large campuses need the high-voltage level, 110 kV in Germany, or extra-high voltage at 220 and 380 kV. The higher the voltage level, the more capacity can be connected, and the more work it takes: a high-voltage connection usually means a dedicated substation on the site.

Point of connection. The network operator names the substation or line the load will be connected to. The distance between that point and the site determines the cost of the tie-in. Who pays is set out in the connection agreement; the norm is a construction cost contribution scaled to the capacity ordered.

Capacity and timeline. A request states the connection capacity and the date from which it is needed. Network operators increasingly question reservations without a concrete project. Whoever holds capacity has to show they will use it.

The legal framework is the German Energy Industry Act (EnWG). Under § 17(1) EnWG, network operators must connect end consumers and storage facilities on terms that are reasonable, non-discriminatory and transparent. Under § 17(2) EnWG they may refuse only where a connection is not technically or economically possible or reasonable, with written reasons; where capacity is short, the applicant can demand information on which expansion measures and costs would make the connection possible. § 17(2b) EnWG also lets network operators offer flexible connection agreements that cap the maximum offtake, statically or dynamically. For data centres that is a tool, not an obstacle: limited capacity early is often worth more than full capacity years later.

Why are sites outside the Frankfurt area coming into view?

Because the grid in the Rhine-Main region is congested in many places, and many workloads do not need to sit next to the internet exchange.

Frankfurt is the centre of the German data centre market, with the DE-CIX internet exchange and dense fibre. That density is now the problem: anyone requesting capacity there competes with everyone else for the same substations.

Demand has changed at the same time. Training AI models, batch processing, backup and much of cloud computing do not react to a few milliseconds of latency. What matters for them is where power is available, renewable and affordable. That makes regions interesting that were not on the map before: sites near extra-high-voltage lines and large substations, former power plant and industrial sites with existing grid infrastructure, regions with high wind and solar generation where the grid needs consumers.

For municipalities outside the metropolitan areas this is a new situation: a data centre brings trade tax, jobs in construction and operation, and a heat source for the local heating network. More on our page for municipalities.

How does an energy-first developer approach this?

By checking the grid before the land, and by planning storage, generation and connection as one system.

Grid first. Before land is secured, the question goes to the network operator: what capacity, at which point, from when. The answer decides whether a site is pursued. Buying land first and asking afterwards means buying a risk.

Battery storage. A battery at the data centre covers load peaks and keeps offtake below the contracted capacity. The same connection carries more IT load, and a flexible connection agreement becomes workable. How this works is the subject of our article on battery storage at data centres.

On-site generation. Photovoltaics on the roofs and open land of the campus, plus long-term power purchase agreements. That reduces grid offtake and helps with an obligation under the German Energy Efficiency Act: from 1 January 2027, operators must cover their electricity consumption 100 percent with renewable electricity on a balance-sheet basis (§ 11(5) EnEfG).

Staged connection. A campus does not go live in one day. The first phase can start at a lower voltage level or with limited capacity while the substation for the final build-out is planned and built. Storage and generation bridge the gap.

Waste heat from the start. Where a heating network is being built or extended, a data centre has an offtaker for its heat, and the municipality has a source. That is a site criterion, not an add-on.

Bright & Green comes from the energy side. The company develops, builds and operates data centres and battery storage, and built its grid and energy expertise over almost twenty years of constructing solar plants. How we plan energy and grid for a campus is described on the page energy and grid. Information for owners of land near a substation or high-voltage line is under land.

Frequently asked questions

How long does a grid connection for a data centre take?

It depends on the point of connection. Where the substation has spare capacity, the work is the study, the contract and the tie-in: months. Where a new substation or line has to be built, planning, permitting and lead times are added, and months become years. That is why the enquiry to the network operator belongs at the start of every site assessment.

Can a data centre operate without a grid connection?

Not for long. On-site generation and storage reduce grid offtake and bridge hours, but they do not replace a connection that carries the load around the clock. A data centre without a grid would be a power plant with servers attached: more expensive, harder to permit and less available.

What is a connection commitment?

The binding statement by the network operator that it will connect a stated capacity at a stated point from a stated date. It follows the grid compatibility study and is detailed in the connection agreement. Without it a site is an intention, not a basis for investment.

Who is the right contact for the grid connection?

The operator of the grid the connection sits in: the local distribution system operator for smaller capacities, the regional transmission system operator for large ones. Capacity and voltage level determine which. An experienced developer has this conversation before talking about the land.